1. Field of the Present Invention
The present invention relates to a signal generation device, and more particularly, a signal generation device used for an information input system capable of inputting information by using an ultrasonic signal and a reference signal.
2. Description of the Related Art
As information and communication technology has been developed, various types of electronic input means substituting for a keyboard and a mouse in the related art have been contrived. As a representative example, much attention has been paid to a method of tracking a position of a signal generation device by using a time difference between a propagation time of a reference signal propagating at the speed of light and a propagation time of an ultrasonic signal propagating at the speed of sound and inputting position information of the signal generation device.
In the information input method using the reference signal and the ultrasonic signal, two or more ultrasonic wave reception sensors which are separated from each other by a predetermined distance and a reception module where a reference signal reception sensor is disposed are installed.
If the signal generation device simultaneously generates the ultrasonic signal and the reference signal (an infrared ray signal, an RF signal, or the like), the reference signal which propagates at the speed of light is received by the reception module at the same time of the generation, and the ultrasonic signal propagates through the air at the speed of sound to be received by the ultrasonic wave reception sensors which are separated from each other by a predetermined distance.
The reception time of the reference signal can be estimated by the generation time of the ultrasonic signal. The distance between the signal generation device and each of the ultrasonic wave reception sensors can be obtained by multiplying the speed of sound with the time taken for the ultrasonic signal to propagate from the signal generation device to each of the ultrasonic wave reception sensors, and the distance between the ultrasonic wave reception sensors is a value which is defined in advance. Therefore, a position of the ultrasonic signal can be measured by the triangulation method. The method of measuring the position of the signal generation device is described in detail in Korean Patent No. 10-0418423, and thus, the detailed description thereof is omitted.
FIG. 1a is a diagram illustrating a configuration of a conventional signal generation device, and FIG. 1b is a detailed diagram illustrating a signal generation module for generating an ultrasonic signal and a reference signal in a conventional signal generation device.
First, referring to FIG. 1a, the signal generation device includes a housing 120, a signal generation module 130 disposed at the front end of the housing, and a cap portion 110 engaged with the housing to contain the signal generation module.
A power supply unit and a microprocessor are built in the housing 120. The power supply unit and the microprocessor is electrically connected to a flexible printed circuit board 133 included in the signal generation module to supply power and control signals to the signal generation module 130.
The cap portion 110 in engagement with the housing protects the signal generation module 130. The ultrasonic signal and the reference signal are emitted in the air through an emission openings 112 formed on the cap portion 110.
The signal generation module 130 generates a reference signal and an ultrasonic signal. Referring to FIG. 1b, the signal generation module 130 includes a spool 132, a flexible printed circuit board 133, a reference signal generation unit 136, an ultrasonic wave generation unit 131, and a contact maintaining member 134.
An electrode pattern is formed on the flexible printed circuit board 133, and the reference signal generation unit 136 is disposed so as to be connected to the electrode pattern. A pair of contact electrodes 137 is formed to be connected to the ultrasonic wave generation unit 131 to supply power to the ultrasonic wave generation unit 131. The reference signal generation unit 136 may be implemented with a pair of LED lamps generating infrared rays. The flexible printed circuit board 133 is engaged with the spool 132 so as to surround the spool 132.
On the other hand, the ultrasonic wave generation unit 131 includes a piezo film 131-1 and conducting points 131-2 formed on the two surfaces of the piezo film to supply a voltage to the piezo film 131-1. As illustrated in FIGS. 1a and 1b, the conducting points are in contact with the respective contact electrodes 137 of the flexible printed circuit board. In addition, the ultrasonic wave generation unit is engaged with the spool so as to surround the spool.
On the other hand, the contact maintaining member 134 exerts pressure on the contact electrodes in the state where the conducting points 131-2 of the ultrasonic wave generation unit are in contact with the contact electrodes 137 so that the contact state between the conducting points 131-2 formed on the two surfaces of the piezo film and a pair of the contact electrodes 137 formed in the flexible printed circuit board are maintained. The contact maintaining member 134 is constructed with a material having good compressibility and restitution elasticity. The contact maintaining member 134 is engaged with the spool 132 by screw engagement through a central engagement hole 134-1. In the process of combining with the spool 132, the contact maintaining member 134 exerts pressure on the contact electrodes by pressure applying portions 134-2 of the two ends of the contact maintaining member 134.
Recently, electronic apparatuses tend to be configured to have small sizes, and the signal generation device also needs to be miniaturized so as to be used for portable electronic apparatuses. However, the aforementioned conventional signal generation device has a difficulty in the miniaturization thereof.
In the conventional signal generation device, in order to connect the ultrasonic wave generation unit 131 to the flexible printed circuit board 133 without influence on the reference signal generation unit 136, the contact maintaining member 134 described above is used. The contact maintaining member 134 needs to has a certain length so as to include an engagement hole 134-1 through which a screw for screw engagement with the spool 132 passes and two-end pressure applying portions 134-2 for applying pressure to a pair of the contact electrodes. In addition, with respect to the position of the reference signal generation unit 136, the reference signal generation unit 136 is disposed to be separated by a certain distance from the contact maintaining member 134 so as to be capable of 360-degree radiation and so as not to interfere with contact maintaining member 134. Therefore, the length of the reference signal generation unit 136 cannot be reduced.
Therefore, there is a physical limitation in reducing the size of the signal generation module.